4inch 800x480 display with capacitive touch for 20€ (UK and Ireland only)

well...kind of...

link

The bad news is that the display does not feature SPI, 8-bit or 16-bit interface we're so used to and which is so easy to wire-up but it features 1GHz dual core CPU, 512MB RAM, 4GB ROM, includes various on-board modules like GSM, Bluetooth 4.0, GPS, WiFi, SD card, Audio Out, Microphone, Camera, FM tuner, USB and has an integrated 1400mAh battery. I think one could actually use it as a phone.

Free shipping within UK if you buy something more for a fiver and you gotta buy two if you want free ship to Ireland. Obviously you can buy it from wherever amazon can ship it to but the postage fee will kick in.
Considering a bare 2.8" 320x240 capacitive touch screen can cost $40, I think this is a pretty decent deal...not for everyone, sometimes you really need that SPI interface and raw access...

Yes, they are great for Bluetooth control pads using free configurable Apps and to monitor web enabled Wifi sensor nodes (ie cheap ESP8266 nodes programmed with the Arduino IDE!).

You can also get 7" Android tablets for £20-£30 now which are a better size for viewing from a distance.